Page 121 - Environment: The Science Behind the Stories

testing your Comprehension

1. In a tropical rainforest, the harpy eagle occupies the 6. Explain primary succession. How does it differ from sec-
emergent layer, Toco toucan the canopy layer, and the ondary succession? Give an example of each.
black-crowned antpitta occupies the shrub layer. Explain 7. Discuss ways to control invasive species.
this phenomenon.
8. What is restoration ecology? Why is it an important sci-
2. Contrast the three main types of exploitative species inter- entific pursuit in today’s world?
actions. How do predation, parasitism, and herbivory differ?
9. What factors most strongly influence the type of biome
3. Give examples of symbiotic and nonsymbiotic mutual- that forms in a particular place on land? What factors
isms. Describe at least one way in which a mutualism determine the type of aquatic system that may form in a
affects your daily life. given location?
4. Compare and contrast trophic levels, food chains, and 10. Draw a typical climate diagram for a tropical rainfor-
food webs. How are these concepts related, and how do est. Label all parts of the diagram and describe all of the
they differ? types of information an ecologist could glean from such a
5. Discuss the interrelationship between great whales, orcas, diagram. Now draw a climate diagram for a desert. How
sea lions, sea urchins, and kelp in the Pacific Ocean. does it differ from your rainforest climatograph, and what
does this tell you about how the two biomes differ?

Seeking Solutions

1. Suppose you spot two species of birds feeding side by 4. Why do scientists consider invasive species to be a prob-
side, eating seeds from the same plant. You begin to won- lem? What makes a species “invasive,” and what ecologi-
der whether competition is at work. Describe how you cal effects can invasive species have? Give examples.
might design scientific research to address this question. 5. Our map of biomes in Figure 4.17 appears to be a perma-
What observations would you try to make at the outset? nent record of stable patterns across the planet. But are
Would you try to manipulate the system to test your the locations and identities of biomes truly permanent, or
hypothesis that the two birds are competing? If so, how? might they change over time? Provide reasons for your
2. Spend some time outside on your campus, in your yard, answers.
or in the nearest park or natural area. Find at least 10 spe- 6. thINk It thrOUGh A federal agency has put you in
cies of organisms (plants, animals, or others), and observe charge of devising responses to the zebra mussel inva-
each one long enough to watch it feed or to make an edu- sion. Based on what you know from this chapter, how
cated guess about how it derives its nutrition. Now, using would you seek to control this species’ spread and reduce
Figure 4.11 as a model, draw a simple food web involving its impacts? What strategies would you consider pursu-
all the organisms you observed. ing immediately, and for which strategies would you
3. Can you think of one organism not mentioned in this commission further scientific research? For each of your
chapter as a keystone species that you believe may be a ideas, name one benefit or advantage, and identify one
keystone species? For what reasons do you suspect this? obstacle it might face in being implemented. What addi-
How could you experimentally test whether an organism tional steps might you suggest to deal with the unfolding
is a keystone species? quagga mussel invasion?

Calculating Ecological Footprints

In 2005, environmental scientists David Pimentel, Rodolfo and damage, as well as costs required for control of the inva-
Zuniga, and Doug Morrison of Cornell University reviewed sci- sive species. (Pimentel’s group did not try to quantify monetary
entific estimates for the economic and ecological costs inflicted estimates for losses of biodiversity, ecosystem services, and
by introduced and invasive species in the United States. They aesthetics, which they say would drive total costs several times
found that approximately 50,000 species have been introduced higher.) Calculate values missing from the table to determine
in the United States and that these account for over $120 billion the number of introduced species of each type of organism and
120 in economic costs each year. These costs include direct losses the annual cost that each inflicts on our economy.

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